With recent development in mobile phones including smartphone, many investigations have been made on methods of fabricating an antenna inside the mobile phones. There has been a particular need for enabling three-dimensional design of the antenna inside the mobile phones. Laser direct structuring (occasionally referred to as “LDS”, hereinafter) having attracted public attention is one of known methods of forming such three-dimensional antenna. LDS is a technique of forming a plated layer, typically by irradiating laser to the surface of a resin molded article that contains an LDS additive, to thereby activate only a portion irradiated by the laser, and then by applying a metal to the activated portion. A feature of the technique is that a metal structure, such as antenna, may be fabricated directly on the surface of a resin base, without using an adhesive or the like. The LDS technique is disclosed for example in Patent Literatures 1 to 4.
Patent Literature 5 discloses conductor tracks placed on an electrically non-conductive supporting material, which are comprised of metal nuclei and of a metallization subsequently applied thereto, whereby the metal nuclei are produced by using electromagnetic radiation to break up electrically non-conductive metal compounds contained in the supporting material in a dispersed manner. The electrically non-conductive metal compounds are formed from insoluble inorganic oxides, which are highly stable with regard to heat, stable in an acidic or alkaline aqueous metallization bath, and which are higher oxides having the spinel structure, or are simple-d-metal oxides or mixtures thereof, or mixed metal compounds having spinel-like structures, and these metal compounds remain unchanged in unirradiated areas. Patent Literature 5 also describes a process of coating the electrically non-conductive higher oxides on a structural member to forma cover layer, allowing the cover layer to release heavy metal nuclei upon being irradiated by electromagnetic radiation selectively in a region where the conductor tracks will be formed, and then chemically reducing the region to metallize it.